1. Field of the Invention
The present invention is generally related to a hydraulic system for a marine vessel and, more particularly, to a hydraulic system that uses two alternative motive devices to drive a hydraulic pump which maintains a preselected pressure in a hydraulic system to which a plurality of hydraulic components are connected.
2. Description of the Prior Art
Many different types of hydraulic systems are known to those skilled in the art.
U.S. Pat. No. 4,265,192, which issued to Dunn on May 5, 1981, describes an auxiliary hydraulic maneuvering system for small boats. A hydraulic pump driven by any suitable power source, such as by an electric motor energized from a storage battery, supplies water under hydraulic pressure by way of a control valve unit to a plurality of pairs of downwardly and outwardly-inclined nozzles disposed at various locations around the boat's hull above the water line thereof.
U.S. Pat. No. 6,554,662, which issued to Hedlund et al. on Apr. 29, 2003, describes a hydraulic system in a boat hull, preferably a boat hull having an outboard drive. An hydraulic installation in a boat hull is described for swinging a propeller rig pivotably suspended in a shell on a boat transom using a piston-cylinder device arranged in a hydraulic control circuit. A control valve included in the hydraulic circuit for controlling the flow to and from the hydraulic cylinder is sealingly mounted in a through-opening in the shell, so that one side of the valve faces outwardly towards the propeller rig in order to be subjected to water spray during driving and serve as an oil cooler.
U.S. Pat. No. 5,476,400, which issued to Theophanides on Dec. 19, 1995, describes a hydraulic power system for a boat. The system comprises a marine thruster assembly. A structure is for mounting the marine thruster assembly to an external surface of a transom on the boat. A first hydraulic operative facility is for propelling the marine thruster assembly, so that the boat can travel in a body of water. A second hydraulic operative facility is for steering the marine thruster assembly, so that the boat can be directed on a course in the body of water. A third hydraulic operative facility is for lifting the marine thruster assembly out of the body of water for inspection and repair when needed.
U.S. Pat. No. 4,698,035, which issued to Ferguson on Oct. 6, 1987, describes a marine propulsion device hydraulic system. The device comprises a propulsion unit adapted to be pivotally mounted on the transom of a boat for pivotal movement relative to the transom about a steering axis, the propulsion unit including a rotatably mounted propeller, an engine including a throttle lever, and a shiftable transmission drivingly connecting the engine to the propeller and including a shift lever, a hydraulic shift assist system connected to the shift lever for actuation thereof, a hydraulic throttle assist system connected to the throttle lever for actuation thereof, a hydraulic fluid reservoir, a pump communicating with the reservoir, a supply conduit communicating between the pump and the shift assist system, a supply conduit communicating between the shift assist system and the throttle assist system, and a return conduit communicating between the throttle assist system and the reservoir.
U.S. Pat. No. 6,547,610, which issued to Kim on Apr. 15, 2003, describes a parallel-operated hydraulic motor type stern propulsion apparatus for boats and hydraulic system for controlling the same. The parallel-operated motor type stern propulsion apparatus for boats and hydraulic system is described. The stern propulsion apparatus includes a transom box disposed at the stern of a boat. A propulsion body situated in the transom body to be lifted and steered is described in combination with the propulsion body which includes an upper body supported by a lifting shaft transversly fitted into the transom box, a yoke connected to the lower body, and two lower bodies each attached to each of the lower ends of the yoke.
U.S. Pat. No. 6,273,771, which issued to Buckley et al. on Aug. 14, 2001, discloses a control system for a marine vessel. The control system incorporates a marine propulsion system that can be attached to a marine vessel and connected in signal communication with a serial communication bus and a controller. A plurality of input devices and output devices are also connected in signal communication with the communication bus and a bus access manager, such as a CAN Kingdom network, is connected in signal communication with the controller to regulate the incorporation of additional devices to the plurality of devices in signal communication with the bus whereby the controller is connected in signal communication with each of the plurality of devices on the communication bus. The input and output devices can each transmit messages to the serial communication bus for receipt by other devices.
U.S. Pat. No. 3,914,939, which issued to Purdy on Oct. 28, 1975, describes a pressure compensated pump. A control circuit for regulating the output of a variable displacement pump in response to the total demand called for by a plurality of manually operable fluid motor control valves is described. Each motor control valve has an associated flow control valve connected in series with it. The flow control valves are connected in series with each other, each dividing the flow which it receives between its associated motor control valve and the next downstream flow control valve.
U.S. Pat. No. 6,341,623, which issued to Channing on Jan. 29, 2002, describes a variable orifice, pressure compensated automated fuel jet pump. The pump is provided with a first chamber having a rear end sealed from a front body by a pressure communicative boundary. The first chamber front end has an inlet fluidly connected with a source of pressurized fluid. The first chamber front end also has a nozzle outlet. A second chamber is provided having a first inlet fluidly connected with the first chamber outlet. The second chamber has a second inlet fluidly connected with a sump. The second chamber has a delivery outlet. A valve member is operatively associated with the first chamber boundary for controlling a flow from the first chamber inlet through the first chamber outlet. A position of the valve member with respect to the first chamber outlet is responsive to a pressure differential between the first chamber front end and the rear end.
U.S. Pat. No. 3,784,326, which issued to Lagana et al. on Jan. 8, 1974, describes a pressure compensated pump. A constant pressure fluid source is provided by operating a balanced variable displacement vane pump as a pressure compensated device. The pressure differential across the pump is sensed and employed to hydraulically and automatically control pump displacement by adjusting the position of the movable seal blocks with respect to the rotor to thereby regulate flow in the interest of maintaining the desired output pressure.
U.S. Pat. No. 4,289,452, which issued to Kubilos on Sep. 15, 1981, describes a pressure compensated pump. The pump has a pressure compensator valve connected to a stroking piston. When the discharge pressure exceeds a set maximum, the compensator valve connects pressure fluid to the stroking piston to reduce the displacement of the pump. The flow of pressure fluid to the stroking piston is accompanied by a concurrent flow of fluid to case.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In a marine vessel hydraulic system, those skilled in the art are familiar with many devices that are operated through the use of hydraulic pressure. However, marine vessel hydraulic systems typically utilize numerous hydraulic pumps which are each designated to operate one hydraulic device. As an example, a hydraulic pump can be driven by a belt system connected in torque transmitting relation with the crankshaft of an internal combustion engine. Alternatively, some hydraulic devices are provided with an individual hydraulic pump driven by a dedicated electric motor. In a typical arrangement, a hydraulic pump used for a hydraulic steering system is driven by belts connected to the internal combustion engine. The power trim system of the marine propulsion unit is typically driven by a hydraulic pump that is operated by a dedicated electric motor connected to a battery. When the internal combustion engine is not operating, stand alone hydraulic pumps are driven by stand alone electric motors to provide hydraulic pressure to operate various systems, such as the power trim system which is needed to raise the marine propulsion device upwardly relative to the transom of the boat.
It would be beneficial to the hydraulic system of a marine vessel if a single hydraulic system could be provided with a single pressure compensated pump that can supply hydraulic pressure to numerous hydraulic devices on the marine vessel. This would provide savings and avoid the redundant provision of numerous hydraulic pumps which are each dedicated to their own motive device.